Axial type hydrodynamic machine



w. FERRIS I 2,661,701

AXIAL TYPE HYDRODYNAMIC MACHINE l4 Sheets-Sheet l Dec. 8, 1953 Filed Oct. 5. 1947 INVENTOR WALTER FERRIS Z B. on 09 m LzA vw ATTQRNEY Dec. 8, 1953 w. FERRIS AXIAL TYPE HYDRODYNAMIC MACHINE Filed Oct. 3. 1947 14 Sheets-Sheet 2 INVENTOR WALTER FE-RRIS ATTORNEY Dec. 8, 1953 w. FERRIS 2,661,701

AXIAL TYPE HYDRODYNAMIC MACHINE Filed Oct. 3, 1947 14 Sheets-Sheet 3 INVENTOR WALTER FERRIS ATTORNEY Dec. 8, 1953 w. FERRIS 2,661,701

AXIAL TYPE HYDRODYNAMIC MACHINE Filed Oct. 3. 1947 14 Sheets-Sheet 4 INVENTOR WALTER FERRIS BY I ATTORNEY Dec. 8, 1953 Filed Oct. 5, 194

W. F ERRIS AXIAL TYPE HYDRODYNAMIC MACHINE 14 Sheets-Sheet 5 INVENTOR WALTER FERRIS TORNEY Dec. 8, 1953 w. FERRIS 2,661,701

AXIAL TYPE HYDRODYNAMIC MACHINE Filed Oct. 3, 1947 14 Sheets-Sheet 6 9 INVENTOR 74 W LTER FEVRRIS ATTORNEY Dec. 8, 1953 w, FERRls 2,661,701

AXIAL TYPE HYDRODYNAMIC MACHINE Filed Oct. 5. 1947 14 Sheets-Sheet '7 WALTE ERRIS ATTORNEY Dec 8 1953 RRRR Is HYDRODYNAMIC MACHINE Filed Dec. 8, 1953 w. FERRIS AXIAL TYPE HYDRODYNAMIC MACHINE l4 Sheets-Sheet 10 Filed Oct. 3. 1947 mo 1 M Lt ATTORNEY W. FERRIS AXIAL TYPE HDRODYNAMIC MACHINE Dec. 8, 1953 14 Sheets-Sheet 13 Filed Oct. 5. 1947 ATTORNEY Dec. 8, 1953 w. FERRIS 2,661,701

AXIAL TYPE HYDRODYNAMIC MACHINE Filed Oct. 5. 1947 14 Sheets-Sheet 14 ERRIS ATTORNEY INVENT WALTER F mw flhm UN V v x Patented Dec. 8, 1953 2,661,701 AXIAL TYPE HYDRODYNAMIC MACHINE I Walter Ferris, Milwaukee, Wis., assignor to The Oilgear Company, Milwaukee, Wis., a. corporation of Wisconsin Application October 3, 1947, Serial No. 777,794

26 Claims. (01. 103-162) This invention relates to rotary hydrodynamic machines of the type having a rotatable cylinder barrel, a plurality of pistons and cylinders arranged in the cylinderbarrel around and parallel to its axis of rotation and a rotatable thrust member which cooperates with the pistons and is inclined to the cylinder barrel axis when the machine is performing useful work.

Such'a machine will function as a pump when driven mechanically and it will function as a motor-when supplied with motive liquid but, since the functions of a pump and the functions of a motor are substantially opposite to each other, the machine will be referred to herein as a pump in order to simplify the description of a machine in which the invention is embodied but it is to be understood that the term pump as'used' herein means a hydrodynamic machine regardless of whether the machine functions as a pump or as a motor. For the purpose of illustration, the invention has been shown embodied in an angle type axial pump but certain features of the invention are applicable to other types of axial pumps.

The present invention has as an object to provide an axial type pump which when operating at high pressures will have a higher overall elliciency thanthe prior axial type pumps.

Another object is to provide an axial type pump capable of delivering liquid at very high pressures and at very large volumetric rates relative to the size of the pump.

Another object is to provide hydraulic means for limiting the axial thrust upon the bearings which support the rotatable parts.

Ihe flow of liquid to'and from the pumping cylinders of an axialtype pump is ordinarily controlled by a flat valve which engages the end of the cylinder barrel and is provided with two ports with which the cylinder ports register alternately during operation of the pump. When the pump creates pressure, the liquid in theports and in the lubricating film between the valve and'the cylinder barrel exerts a blow-off force which tends to move the cylinder barrel. away from thevalve.

Another object of the present invention is to provide hydraulic means in addition to the pumping pistons for exerting a hold-up force upon the cylinder barrel in opposition to the blow-off force. Another object is to provide an axial typepump with a main flat valve and an auxiliary flat valve which together control the flow of liquid to and from the pumping cylinders "and the auxiliary valve also applies a hold-up force to the cylinder barrelin opposition to the blow-off force exerted 2 by the liquid between the main valve and the end of the cylinder barrel.

Another object is to provide an angle type pump having novel means for varying its displacement.

Another object is to provide an angle type pump with hydraulic means for relieving the thrust member bearing from the greater part of the axial thrust imposed thereon when the pump is creating pressure.

Another object is to provide an axial type pump in which the pumping pistons are connected to the thrust member through universal joints which are lubricated in a novel manner.

Another object is to provide an axial type pump in which the cylinder barrel is driven through a universal joint and novel means are provided for lubricating that joint.

Other objects and advantages will be apparent from the following description of the embodiments of the invention shown in the accompanying drawings in which the views are as follows:

Fig. 1 is a central vertical longitudinal section through a pump in which the invention is embodied, the view being taken on the line l! of Fig. 2 and showing the pump adjusted to'deliver liquid in one direction. w

Fig. 2 is a central sectional planview taken'on the lines 2--2 of Figs. 3 and 4 but showing the pump adjusted to zero displacement, certain parts being broken away and omitted in order that the view may be on the same scale as Fig. 1.

Fig. 3 is a transverse vertical section taken on the irregular line 3-3 of Fig. 2.

Fig. 4 is a transverse vertical section taken on the line 4-4 of Fig. 1

Fig. 5 is a face view of the valve for controlling the flow of liquid to and from the pumping cylinders, the view being taken on the line 5-5 of Fig. 1 but drawn to a larger scale.

Figs.6 and 7 are-sectionalviews takenthrough the valve and portionsof the adjacent parts, the planes of the views being indicated, respectively, by the linesG-t and 7+! of Fig. 5; V

Fig. 8 is a transverse section showing the arrangement of the'cylinders'in the cylinder barrel and the face of 'a valve-like hold-up element which assists in holding the ends of the cylinder barrel against the faceof the valveshown in Fig. 5, the view being taken inthe plane indicated by the line 8-8 of Fig. 1 but drawn to a larger scale.

Figs. 9 andlO aresections through the valvelike hold-up element andf.portion's of the adjacent parts, the viewsbe ing taken on'the lines.9''9 and like! ofFigfiB.

Fig. 11 is a transverse section taken on the line of Fig. 1 but drawn to a larger scale.

Fig. 12 is an enlarged sectional view of one of universal joints for connecting the pumping pistons to the thrust member which causes the pistons to reciprocate when the pump is driven.

Fig. 13 is a section taken on the line Iii-l3 of Fig. 12 but drawn to a still larger scale.

Fig. 14 is an end view of the thrust member which causes the pistons to reciprocate when the pump is driven, the View being taken in the plane indicated by the line of Fig. l but drawn to a larger scale.

Fig. 15 is a transverse sectional View taken on the irregular line |---|5 of Fig. l but drawn to a larger scale and showing a valve-like hold-up element for exerting upon the thrust member forces counter to the pumping forces.

Fig. 16 is a section through the valve-like holdup element shown in Fig. and portions of the adjacent parts, the view being taken on the line |6|$ of Fig. 15.

Fig. 17 is a sectional View showing a connection through which liquid is supplied to the valve-like hold-up element shown in Fig. 15, the view being taken on the line |l-| l of Fig. 1.

Fig. 18 is an end view of the pump looking toward the left hand end of Fig. 1.

Fig. 19 is a longitudinal section taken through a portion of the pump on the irregular line i9-| 9 of Figs. 3 and 18.

Fig. 20 is a longitudinal section taken through a portion of the pump on the irregular lines 2 |l--2 3 of Figs. 3 and 18.

Fig. 21 is a section taken on the irregular line 2 |-2l of Fig. 18.

Fig. 22 is a section taken on the line 22-22 of Fig. 18 but drawn to a larger scale.

Fig. 23 is a schematic drawing illustrating the hydraulic circuit of the pump.

Fig. 24 is a schematic drawing illustrating the mechanism for controlling the pump.

Fig. 25 is a longitudinal section through a portion of a pump in which the valve-like hold-up element shown in Figs. 1, 2 and 8 is replaced by an auxiliary valve which urges the cylinder barrel against the main valve and also provides ports and passages for the flow of liquid to and from the pump cylinders so that the ports and passages in the main valve may be correspondingly reduced in size, the plane of the view being indicated by the irregular line 225 of Fig. 8.

General arrangement The pump chosen for illustration has its mechanism enclosed by a housing 5 having webs or ribs arranged therein and two trunnions 2 and 3 (Fig. 3) fixed in its side walls in axial alinement with each other. Housing 1 is adapted to be supported upon a tank or reservoir 3 from which the pump is supplied with liquid. Reservoir d has not been illustrated in detail but is shown diagrammatically in Figs. 23 and 2e.

Trunnions 2 and 3 pivotally support a hollow cradle or yoke 5 having two integral arms 5 and 5* formed upon opposite sides thereof and an end wall or head 5 rigidly secured to its rear or right hand end and forming a fluid tight joint therewith. Arms 5 and 5 are pivoted upon trunnions 2 and 3 respectively, and a bearing 6 is arranged between each arm and the trunnion upon which it is pivoted.

Yoke head 5 is of substantial thickness and it has an integral hub 1 extending from its inner or forward face. A horn 8 is rigidly secured in hub d 1 and head 5 upon the axis of yoke 5 to rotatably support an annular cylinder barrel 9 having an annular head 9 arranged upon its rear end, a bearing being arranged between cylinder head 9 and horn 8.

Cylinder barrel 9 and its head 9 are ordinarily made as separate parts for convenience in manufacturing and the two parts are rigidly secured to each other to form a fluid tight joint thcrebetween. The rear face of end head 9 engages an annular fiat valve l2 which extends around hub '1 between cylinder head B and yoke head 5 to control communication between the cylinders in cylinder barrel 9 and opposite sides of a hydraulic circuit as will presently be explained.

Cyliinder barrel 9 has a plurality of cylinders I5 arranged therein around and parallel to its axis of rotation and a piston 16 is fitted in each cylinder. Each piston I6 is connected by a ball and socket joint H to a thrust member i8 which is supported by a bearing l9 from a web 2|) of housing I. Thrust member I8 is fixed to the inner end of a drive shaft 2| which extends through the front or left hand wall of housing for connection to a source of power.

Rotation is imparted from shaft 2| to cylinder barrel 9 through a universal joint 22 having the front or driven part thereof fixed for rotation with shaft 2| and the rear or driving part thereof fixed to the inner part 23 of an Oldham coupling the outer part 2% of which is fixed to the outer end of cylinder barrel 9. A bearing 25 is arranged between horn 8 and the outer part 2 3 of the Oldham coupling so that cylinder barrel 9 is supported by bearings II and 25 for rotation upon the axis of born 8. The rear part of universal joint 22 is provided with a tail shaft 26 which has its rear end journaled in a bearing 27 arranged within horn 8 and which holds the axis of the rear part of universal joint 22 upon the axis of cylinder barrel 9.

The arrangement is such that when shaft 2| is rotated, cylinder barrel 9 will be rotated from shaft 2| through universal joint 22 and Oldham coupling 2324. The rear face of thrust member 18 rotates in a plane normal to the axis of shaft 2| and, if the axis of cylinder barrel 9 is inclined to the axis of thrust member 18 by tilting yoke 5 upward as shown in Fig. 1 or by tilting yoke 5 downward, thrust member It will reciprocate pistons id in their cylinders during rotation of thrust member |8 but, if the axis of cylinder barrel 9 is coincident with the axis of thrust member N, no reciprocation of pistons It will occur.

Yoke 5 is adapted to be tilted upon trunnions 2 and 3 and held in adjusted positions by hydraulically actuated pump displacement varying means to be presently described. Liquid for operating the displacement varying means may be supplied from any suitable source such as a gear pump having its two gears 28 and 29 arranged in a suitable chamber formed in a gear pump housing 30 which. is fixed within main housing and has a cover plate 3| to enclose the gears within the chamber as shown in Fig. 1. Gear 28 is fixed upon shaft 2 and gear 29 is mounted upon a shaft 32 which is carried by housing 38 and its cover plate 3|. Gear pump housing 36 carries a bearing 33 which with bearing i9 rotatably supports shaft 2|.

7 Cylinder barrel, value and hold-up means As previously explained, cylinder barrel 9 contains a. plurality of cylinders i5, eleven being shown in Fig. 8. A passage 36 (Figs. 1 and 11) extends from the" inner or rear end or eachcylinder '|5 through cylinder head 9 the rear-face of which constitutesa seatfonvalve 12. Liquid flows through passages 36'; to andfrom cylinders l5 and the pressurein that liquid creates a blowon force which tends to separate the cylinder barrel" and the valve as will presently be explained. Sincethe'blow-off force is substantially proportional to the area. of the valve in contact witli'the cylinder barrel, each passage 36 'is extended inward and rearward at an angle to the cylinder axis and then extended rearward in order that the contact face of valve l2 may be as small as practicable. The rear ends of passages 36 are elongated'in a circumferential direction to forrricylinder ports as shown in Fig. 11.

During rotation of cylinder barrel 5, each passteeper sage 36 will register successively with two arcuate ports 31 and '38 (Figs. 5 and "7 which are formed in valve l2 and extend inward from the contact face thereof. A plurality of holes 39-extend rearward'from the bottom of port 31 and an equal number of holes 46 extend rearward from the bottom of port 38. Each hole 39 communicates witha' hold-up motor 4| which is arranged within valve l2 and each hole 40 communicates with a hold-up motor 42 which is arranged within valve l2. Each hold-up motor 4| communicates with a hole 43 which is formed in yoke head 5 and each hold-up motor 42 communicates with a hole 44 which is formed in yoke head 5. All of the holes 43 communicate with a chamber 45 (Figs. 4 and 2) which is -formed in yoke head 5 upon one side'of the pump centerline, and all of the holes 44 communicate with a chamber 46 which is formed in'yoke head 5 upon the other side of the pump centerline.

Hold-up motors 4| and 42 are identical and each includes a cylinder 41 (Fig. 7) which is formed, in valve l2 in alinement with a hole 39 or 4|], a hollow piston 48 which is fitted in cylinder 41, an, annular sealing member 49 which is arranged between piston '48 and yoke head 5 and is concentric with piston 48 and with a hole 43 or 44', and a spring 50 which is arranged between piston 4s and the end wall of cylinder 41 to urge valve l2 against end head 9 and to urge piston 48 against sealing member 49' and sealing member 49 against yoke head 5. The rear end of'sealing member 49 and the front face of yoke head 5 adjacent hole 43 or 44 are made fiat and smooth and the'fro'nt end'of sealing member 49 and the rear end of piston 48 are made spherical and' smooth to form substantially liquid tight joints therebetween. r The adjacent ends of ports 31 and38 are spaced apart "an angular distance equal to or slightly greater than the angular'length of a passage 36 to 'providetwo sealing arcs or bridges 5| and 52 which" constitute seals between the two ports.

When cylinder barrel 9 is rotated; each piston IE will be drawn outward during one-half of each revolution of cylinder barrel 9 and it will be'forced' inward during the other half of each revolution of cylinder barrel 9 as will presently beexpl'ained; If yoke 5 is tilted upward as shown in Fig. 1, each outward moving piston It will draw liquid into its cylinder l5 through the passage36-conhected thereto, port 31, holes 39, holdup motors 4| and holes 43 from chamber 45 during-thetime the passage 36 is in communication with port 31 then the liquid will momentarily be. trapped in the cylinder as the passage 36 passes across bridge 5|, and then the piston. as it moves outward will eject. liquidfrom its-cylinder through the passage- 36; port 38, holes 40; hold-'- up motors 42 and holes-Mints chamber 46. If yoke 5 is tilted downward or if cylinderbarrel 9 is rotated in the opposite direction, the how of liquid will be reversed.

Liquid will escape at'a minute rate from the high pressure port 31 or 38 and form a lubricating film between the contact face of valve I2 and end head 9. The pressure in the lubricating film will be equal to pump pressure at the edges of the high pressure port 37 or 33, it will gradually decrease'to zero at the inner and outer edges of the valve face adjacent the high pressure port and the pressure will be substantially zero in the film adjacent the low pressure port.

When'the pump i creating pressure, the liquid in the lubricating film adjacent the high pressure 'port and the liquid in the high pressure port will exert a blow-off force which tends to move valve l2 and cylinder head 93* away from each other and which is proportional to pump pressure at any given position of cylinder barrel 9. However, the same pressure extends into the hold-up motors 4| 'or' 42 on the high pressure side of the pump and causes them to urge valve |2 against cylinder head 9 with a force proportional to pump pressure.

The pump is ordinarily provided with an odd number of cylinders. Therefore, the number of passages 36 containing liquid under pressure will vary by one each time the outer end of a passage 36 passes from one to the other of the two valve ports 31 and 38. This variation in the number of passages 36 containing liquid under pressure causes the blow-off force to vary in magnitude and the center of the blow-off'force to shift.

In order to compensatefor' the variations in the magnitude and center of the blow-ofi' force, the hold-up motors are so located and are provided in such numbers and sizes that the sum of the hold-up forces exerted by the hold-up motors on the pressure side of the pump is slightly in excess of the total blow-off force and the resultant of the hold-up forces is approximately coincident with the center'of theblow-ofi force when the minimum number of passages '36 contain liquid under pressure, and the pump is provided with balancing motors at least one of which is momentarily energized and exerts a hold-up force each time the number-of passages 36 containing liquid under pressure changes from minimum to maximum and the balancing motors are so located and ofsuch size and number that the sum of the hold-up forcesexerted by the energized holdup andbalancingmotors is slightly in excess of the total blow-01f force and the result ant of the hold-up forces is approximately coincident with the center of the blow-off force when the maximum number or passages 36 contain liquid under pressure. I

For the purpose of illustration, the piunphas been shown in Figs. 5 and 6 as being provided with two balancing motors but the'number may be varied according to requirements. One of the balancing motors includes a cylinder 53 which is formed in valve 12 behind bridge 5| and a piston 54 which is fitted in cylinder 53 and engages yoke head 5 The other balancing motor includes a cylinder '55 which is formed in valve |2 behind bridge 52 and a piston 58 which is fitted in cylinder 55 and engages yokehead 5. Ducts 51" and 58 extend, respectively, from cylinders '53 and 55 through the faces of bridges El and 52 into the path of passages*36?so that-eachbalanc ing motor is. energized? eachtime ai'aassage-tli containing pressure registers with the duct 51 or 58 leading to that motor.

The arrangement is such that when the pump is operating, the hold-up motors 4| or 42 on the high pressure side of the pump are continuously energized and exert the entire hold-up force when the minimum number of passages 38 contain liquid under pressure at which time the blow-off force is minimum. Each time a passage 36 passes from the high pressure port 31 or 38 onto a bridge 5| or 52, the pressure in that passage increases the magnitude and shifts the center of the blow-off force but, as soon as that passage opens slightly to the duct 5'! or 58 in that bridge, the balancing motor 53-54 or 55-58 behind that bridge is energized and thereby increases the magnitude and shifts the center of the hold-up force. As soon as that passage opens slightly to the low pressure port, the blow-off force is correspondingly decreased and the balancing motor is deenergized.

Likewise, each time a passage 36 is passing from the low pressure port across a bridge 5i or 52 opens slightly to the high pressure port, the liquid in that passage is suddenly compressed and increases the magnitude and shifts the center of the blow-off force but that passage is at that time in registry with the duct 5'! or 58 in that bridge so that the balancing motor 53-54 or 5556 behind that bridge is energized and thereby increases th magnitude and shifts the center of the hold-up force until the following passage 35 registers with the same duct and thereby de-energizes the balancing motor. The

hold-up force is thus increased when the blowolf force increases and is decreased when the blow-ofi force decreases.

When the pump is discharging liquid and is creating pressure, the blow-off force urges cylinder barrel 9 toward the left in respect to Fig. 1,

and the liquid in the cylinders l6 containing pressure acts upon the inner ends of those cylinders and exerts thereon forces which may be designated as pumping forces and which urge cylinder barrel 9 toward the right in opposition to the blow-oil force.

If the pump were supercharged, that is, if liquid were supplied to the intake of the pump at a substantial pressure, the ports and passages in valve l2 would need to be only large enough to permit the required volume of liquid to flow therethrough at a high velocity. Therefore, the valve face subjected to pressure could be kept at a minimum so that the blow-off force would be minimum and the difference between the blowofl force and the sum of the pumping forces would not be great enough to impose an excessive load upon the cylinder barrel bearings.

However, it is not practical to supercharge a pump having a substantial volumetric capacity and, in order that the pump may draw enough liquid through the valve to completely fill its cylinders, the ports and passages in the valve must be large enough to permit that liquid to flow therethrough at a low velocity. Ports and passages of such large size require that the contact face of the valve be considerably larger than would be necessary if the pump were supercharged. With the face of the valve having such a large area subjected to pressure, the blow-off force is greatly in excess of the pumping forces.

If no other means were provided, the blow-off forc in excess of the sum of the pumping forces would impose so large an axial thrust upon the cylinder barrel bearings that it would be necessary to-employ bearings so large that the chi-- ciency of the pump would be greatly reduced. In order to keep the efficiency as high as possible and to avoid the wear and eventual destruction resulting from imposing large axial thrusts upon mechanical bearings, the pump is provided with hydraulic means which exerts a.

force in opposition to the blow-off force. The hydraulic means also functions as a liquid bearing which is far more efiicient than a mechanical bearing.

As shown in Figs. 1 and 2, the annular inward portion of cylinder head 9 is engaged by an annular valve-like hold-up element 64 which extends around horn 8 and is arranged within the annular inner wall of the body portion of cylinder barrel 3. The pistons of the hold-up and balancing motors, which are arranged within element fi l as will presently be described, react against an annular abutment 55 which is fixed upon horn & within the annular inner wall of cylinder barrel 8 and is prevented from moving toward the left in any suitable manner such as by engagement with a shoulder formed upon horn 8. Two diametrically opposed pins are fixed in abutment 55 and extend into element 6 to restrain it from radial movement while permitting the rear face of element E4 to adjust itself to the front face of cylinder head 9 Element ea is similar to but is smaller than valve 22. If it were to function also as a valve as illustrated in Fig. 25, it could be the same as valve i2 except that it would be smaller. As shown in Figs. 8 and 9, element 54 has two arcuate ports 67 and 58 formed in the rear face thereof, four holes 69 and four holes Hi extending inward from the bottoms of ports 61 and 68 respectively into communication with four holdup motors ii and 52 respectively. Port 61 and hold-up motors H in element M are opposed to port 37 and hold-up motors Al in valve 12, and port 68 and hold-up motors 12 in element 54 are opposed to port 38 and hold-up motors t2 in Valve i2.

Each of hold-up motors H and '52 includes a cylinder '53 (Fig. 9) which is formed in element 6:3, a piston l5 which is fitted in cylinder '53 and engages abutment 55, and a spring l5 which is arranged between piston M and the rear wall of cylinder 13. Springs i5 urge pistons 14 against abutment G5 and urge element 65 against cylinder head 9 and cylinder head 9 against valve 12.

Element 6 3 is also provided with balancing motors which correspond to the balancing motors 535t and 5555 in valve l2. As shown in Figs. 8 and 10, one balancing motor has its piston "is fitted in a cylinder T! which is formed in element as and has a duct 58 extending therefrom through the rear face of element 64 at a point between the upper ends of ports 81 and 68, and the other balancing motor has its piston it fitted in a cylinder 89 which is formed in element 54 and has a duct 8| extending therefrom through the rear face of element 64 at a point between the lower ends of ports 51 and 68.

Liquid for energizing hold-up motors H and i2 and balancing motors 16-47 and 79-80 is supplied thereto from passages 33 through an equal number of passages 82 each of which, as shown in Figs. 9, l0 and ll, extends from a passage 36 through the front face of cylinder head 9 The front ends of passages 82 are arranged in a circle having the same radius as the circle upon which ports 61 and 68 (Fig. 8) are ar ranged, and the front end of each passage-82 is elongated to a length equal to or slightly less than the angular distance between the adjacent ends ofports 6'5 and 68.

The arrangement is such that, when the cyl-. inder barrel is rotated, passages 82 will register successively with each of ports El and E8 and each of ducts i8 and ti, and each passage 82 will register with one port 81 or 68, then with one duct is or 8| then with the other port 61 or 68 and then with the other duct 18 or 8| during each revolution of the cylinder barrel.

When the pump discharges through port 38 (Fig. hold-up motors 82 will be energized and urge valve I 2 against cylinder head 9 Pressure will extend from the passages on the pressure side of the pump through the passages 82 connected thereto, port 68 (Fig. 8) and holes l8 into hold-up motors l2 and cause them to urge element 64 against cylinder head 9 in opposition to the forces exerted by hold-up motors 42. Each time a passage 35 containing pressure opens to a duct 5'? or 53 (Fig. 5) a balancing motor 5358 or -5t will be energized and cause valve 52 to'exert additional hold-up force uponcylinder head 9 but at the same time that passage 35 opens to duct 5'! or 58, the passage 82 connected to that passage 38 opens to the duct '18 or'8l on the same side of the pump and causesthehold-up motor Tl-l8 or 89-8i to be energized and exert upon cylinder head 9* a force in opposition to the force exerted thereon by balancing motor 53-54 or 55-58. When the pump discharges through port 3'! (Fig. 5), the operation will be the same except that the holdup motors on the other side of the pump will be energized.

The cylinder barrel is thus urged toward the leftby the forces exerted thereon through valve l2 and it is urged toward the right by the pumping" forces and the forces exerted thereon through hold-up element 64. The parts may be so proportioned that the forces which tend to move the cylinder'barrel in one direction at any given instant are substantially counterbalanced by the forces which tend to move the cylinder barrel in the opposite direction at the same instant so that there will be little if any axial thrust upon cylinder barrel bearings H and 25. Preferably, the pump is so constructed that the sum of the forces which tend to move the cylinder barrel toward the left is slightly in excess of the sum of the forces which tend to move the cylinder barrel toward the right and the difference-between the two forces imposes upon bearing 25 an axial thrust which is so slight that it does not increase the friction of the bearing to anyappreciable extent. 7

To minimize the loads on bearings '25 and H upon which cylinder barrel 9 is mounted it'is necessary to take account of the magnitudes and radial locations of the forces imposed'on cylinder head 9 by the pumping pistons l 6, the main valve 42 and the hold-up element 64. In general, the sum of the pumping piston forces and the hold-up force, acting toward the right in respect to Fig. '1, should approximately equal the main valve force acting toward the left. Any excess is taken as an axial thrust on bearing 25 or hearing I I. Also, when the pump is discharging in one direction, thepumping piston force .and the hold-up force tend to tilt the cylinder barrel clockwise, putting a downward radial load on bearingll and an equal upward radial load on bearing 25, and the-main valve force tends to tilt the cylinder barrel counterclockwise, loading the bearings in the opposite directions To minimize the loads on both bearings, these opposing tilting moments should be approximately equal. The magnitude of the valve forces is conditioned by the necessary port areas.

During operation of the pump, liquid escapes in minute quantities from the high pressure ports and passages and forms a lubricating film between the contiguous faces of cylinder head 8 and hold-up element 64. The liquid in ports 61 and 68, and passages 82 and in the lubricatingfilm keeps cylinder head 9 and hold-up element 64 out of metal-to-metal contact with each other and forms therebetween a liquid bearing.

It has previously been pointed out that, ina pump having a large volumetric capacity, it is not practical to restrain the cylinder barrel from axial movement solely by mechanical bearings for the reason that the blow-off force in excess of the sum of the pumping forces is so. great that it would impose an excessive thrust upon the-mechanical bearings. Therefore, the pump may be made in larger volumetric capacities than would be possible if the cylinder barrel were restrained from axial movement solely by mechanical bearings.

Also, since the liquid bearing is far more efficient than a mechanical bearing, a smaller pump provided with a liquid bearing would'require less power to drive it than would be necessary if the cylinder barrel were restrained from axial movement solely by mechanical bearings.

Rotation'of the cylinder barrel tends to cause valve IZand hold-up element 64 to rotate. R0- tation of valve I12 is prevented by two diametrically opposed pins 83' (Fig. 2) which extend into it and into the yokehead 5 valve i2 inthe proper location and they are fitted therein and in'yoke head 5 with sufficient clearance to permit valve l2 to adjust itself to cylinder head'B Element 64 cannot rotate as it is supported by pins 66 from abutment 65 which is fixed upon horn 8 as by being keyed thereto.

' Hydraulic circuit and trunnions As shown in Figs. 2, 3, 4 and 23, the chambers 45 and 46 in yoke head 5 communicate, respectively, with two passages 85 and 86 which extend longitudinally through arms 5 and 5 of yoke 5 and communicate, respectively, with two transverse passages 81. and 88 which are formed in the front end portions of arms 5 and 5 and are in axial alinement with trunnions 3 and 2 respectively. Passages 81 and 83 communicate through trunnions 3 and 2, respectively, with two annular passages 89 and 98 which are formed in opposite side wallsof housing I around trunnions 3 and 2.

Each of trunnions 2 and 3 includes a tubular bearing member 9| which is rigidly secured in a side wall of housing I and has an arm of yoke 5 journaled thereon by means of bearing 6. Member 9! has two tubular pistons or bushings 92 and 93 closely fitted therein to form substantially'fluid tight joints therewith and a plurality of holes 94 formed in its side wall between the adjacentends of'bus'hings 92 and 93 to'provide communication between its interior and theannular passage 89 01-88 which extends around it.

The innerend'of bushing 92 engages an emular sealing member 95 which engages the adjacent arm o'fyoke 5 and'extends around the'pas sage 81 or 88 therein." The abutting facesof Pins 83 supportmember 95 and yoke are made flat and smooth and the abutting faces of member 95 and bushing 92 are made spherical and smooth to form substantially liquid tight joints.

The outer end of bushing 93 is concave and in engagement with the spherical head of a bolt 99 which extends through the adjacent arm of yoke 5 and has a sealing member 91 adjustably secured to its inner end. The outer face of sealing member 91 is convex and in contact with the concave inner face of an annular seat 98 which is rigidly secured in the inner wall of the adjacent arm of yoke 5 and forms a fluid tight joint therewith. The abutting surfaces of members 91 and 98 are made spherical and smooth to form a fluid tight joint.

Bushings 92 and 93 are urged apart by a helical spring 99 which is arranged around bolt 98 and bears against the adjacent ends of bushings 92 and 93. Spring 99 urges bushing 92 against sealing member 95 and sealing member 95 against yoke 5, and it urges bushing 93 against the head of bolt 99. Since inward movement of bushing 92 and sealing member 95 is limited by yoke 5, spring 99 urges bolt 99 outward and thereby urges sealing member 91 against seat 98.

When pressure is created by the pump, it acts upon the adjacent ends of bushings 92 and 93 and augments the force exerted thereon by spring 99. The pressure acts upon the exposed area of sealing member 91 and tends to move it away from its seat 98 but the pressure also acts upon the inner end of bushing 93 and upon the exposed area of the head of bolt 99 and tends to move bolt 99 outward. The area subjected to the outward acting pressure is as great as or is somewhat greater than the area subjected to the inward acting pressure so that the forces exerted by the liquid upon the trunnions are equalized or nearly equalized. Preferably, the parts are so proportioned that the outward acting force is somewhat in excess of the inward acting force so that sealing member 91 is urged against seat 98 by spring 99 and by the difference between the two forces.

The arrangement is such as to provide in effect non-rigid extensions of yoke arms 5*- and 5 into the respective bearing members 9 I Each extension conducts liquid between a yoke arm passage 85 or 89 and an annular passage 89 or 99 and both extensions rotate within bearing members 9! when yoke 5 is swung upward or downward to vary pump displacement. The spherical members 95, 99 and 91 permit deflections of the yoke to occur without aifecting the liquid seals of the hydraulic circuit or causing strain or wear on the sealing members.

Annu ar passages 89 and 99 communicate, respectively, with two passages I93 and I94 which are formed in the walls of housing I and communicate, respectively, with two ports I95 and I96 by means of which the pump may be connected to an external circuit. Passages I93 and I 94 also extend through the bottom wall of housing I for connection to a supply of liquid such as reservoir 4.

As shown in Fig. 23, communication between reservoir 4 and massages I93 and I94 mav be controlled by an automatic suction valve I91 having a valve plunger I98 fitted in the bore I99 of a valve casing II9 which may be attached to the bottom wall of housing I. Valve I91 has two ports I II and I I2 which communicate with passages I93 and I94, respectively,

n a and I 14 with opposite ends of bore 109-. Va ve and which also. communicate, respectively, through two passages I91 also has a port H5 arranged between ports .1

.= the pump when started will discharge liquid through valve I2, holes 44, chamber 46, passage 83, trunnion 2, passages 99 and 194 and port I99 to the external circuit. If valve plunger I98 is in its right hand position, the resistance in the circuit will cause pump pressure to rise and liquid to flow through passage H9 to the right end of bore Hi9 and shift valve plunger I99 to the position shown so that the pump cannot discharge through valve I9? into reservoir 9 when pump pressure becomes high enough to open resistance valve Ill.

The liquid returned from the circuit flows through port I95, passages I93 and 89, trunnion 3, passage 85, chamber 45, holes 93 and valve I2 to cylinder barrel 9. If the liquid returned from the circuit is less than pump requirements, enough liquid to make up the deficiency will be drawn from reservoir 4 through check valve H6 and suction valve I91 into passage I93 where it joins the liquid returned from the circuit. If the liquid returned from the circuit is in excess of pump requirements, the excess liquid will be discharged through passage I93, suction valve I91 and resistance valve II! into reservoir 4. If yoke 5 is tilted downward, the flow will be reversed.

The piston assemblies The piston assemblies chosen for illustration are of the general form shown in Fig. 6 of Patent No. 2,638,859 but they may be one of the other forms shown in that application to which reference may be had for details of construction and an explanation of the advantages of this type of piston assembly.

As shown in Fig. 12, each piston I6 has a bore I2! extending inward from its front end and an annular flange I22 extending around its front end. A connecting rod I23 extends into bore I2I and engages the rear wall thereof. Preferably, the end of rod I23 is spherical and the end wall of bore I2I is flat so that rod I23 can rock upon and make a spot contact with the end wall of bore I2! as the angle between the axis of piston I9 and the face of thrust member I8 changes during rotation of cylinder barrel 9 and thrust member I8.

.As shown in Figs. 12 and 13, each ball and socket joint I1 includes a ball I24, which has its shank I25 fixed in thrust member I 6, and a spherical socket I29 which is fitted to ball I24 and is formed upon connecting rod i23. Ball I24 and socket I29 are arranged within two annular sockets I21 and I29 having projections I29 and I39 formed upon the respective ends thereof so that projections I29 on socket I21 will fit between the projections I39 on socket I29, projections I39 on socket I28 will fit between the projections 129 on socket I21, and the sockets may be fastened together by a snap ring I 3I fitting in an annular groove I32 formed in projections I29 and I39.

The end wall of socket I21 is provided with a spherical surface I33 complementary to and in contact with ball I24, and the end wall of 

